This invention relates generally to an apparatus for logging earth boreholes and specifically to an apparatus which utilizes means to assist a well logging instrument to traverse highly deviated earth boreholes.
It has become relatively common within the last few years to drill wells in the search for oil and gas and the like with a portion of the well bore deviating from the usual vertical orientation thereof. The deviation or inclination may extend for a considerable distance at angles ranging to 70.degree., sometimes returning to the usual vertical orientation.
It is also well known in the art of drilling such wells to attempt the logging of the formations surrounding such boreholes with logging instrument run into the well bore on a wire-line and/or a cable to perform various operations. Such tools usually depend upon the force of gravity to permit positioning of the well tool at the desired location in the well bore.
Another problem associated with such boreholes relates to the instability of some formations penetrated by the well bore, thus causing borehole diameter changes, some very abrupt. Ledges are formed, and the logging instrument frequently will lodge against them.
It is therefore the primary object of the present invention to provide new and improved methods and apparatus for logging earth boreholes, especially those boreholes having abrupt ledges therein.
The objects of the invention are accomplished, generally, by methods and apparatus which utilize means for porting a fluid-reduction agent into the earth borehole to facilitate the movement of the well logging instrument through the borehole. In one embodiment of the invention, a fluid-reduction agent is continually injected into the borehole. In another embodiment, the fluid-reduction agent is ported into the borehole upon some change in conditions, for example, such as a reduction in the velocity of the well logging instrument, or by a manual command from the earth's surface.